1. Technical Field
The present invention relates to an ink set and an image forming method.
2. Related Art
Various techniques are applied to recording methods for forming images on a recording medium, such as paper, according to image data signals. In ink jet techniques of such techniques, images can be formed directly on a recording medium by ejecting an ink only onto desired image portions, using an inexpensive apparatus. Accordingly, ink jet techniques can efficiently use inks and reduce running costs. In addition, little noise is produced when the ink jet technique is used, and the ink jet technique is thus advantageous as a recording method.
In recent years, approaches using an ink jet technique have been attempted for forming glossy images having high water fastness and rub fastness on the surface of a recording medium by ejecting an ink onto a recording medium.
For example, JP-A-2010-120990 discloses a technique for printing on plain paper using an ink jet recording ink containing 40.0 parts by weight of carbon black pigment dispersion (pigment content: 20%), 5.5 parts by weight of glycerol, 16.5 parts by weight of 1,3-butanediol, 2.0 parts by weight of 2-ethyl-1,3-hexanediol, 2.5 parts by weight of fluorochemical surfactant (solid content: 40%), 10.0 parts by weight of self-emulsifying polyurethane resin emulsion (solid content: 30%), 6.0 parts by weight of carboxy-modified methylmethacrylate-butadiene copolymer resin (MBR, solid resin content: 50%), and 17.0 parts by weight of distilled water (paragraph 0030, Example 1).
JP-A-2001-106951 (paragraphs 0042 to 0044, and 0052) discloses a technique for printing on plain paper using an ink jet aqueous pigment ink prepared by adjusting a mixture of materials to 1000 g with ion exchanged water, the materials including 167 g of yellow pigment dispersion (average particle size of the pigment, 75 nm), 71.4 g of latex (Nipol SX 1503 produced by Zeon Corporation, average particle size: 60 nm, content: 3% by weight), 200 g of ethylene glycol, 120 g of diethylene glycol, 4 g of wetting agent (Olfine 1010 produced by Nissin Chemical Industry), and 2 g of preservative (Proxel GXL produced by Zeneca).
However, images formed with the black or yellow ink of the above-cited patent documents on plain paper by an ink jet recording method may crack or stain and thus be nonuniform, and may be poor in color developability.